The present invention relates to a semiconductor device, including any of an insulating coupler for insulating and separating circuit regions and for transmitting electrical signals, an isolator using the same, and an application circuit using the isolator wherein terminals are insulated and separated.
In a case when plural circuits should be insulated electrically for ensuring safety and for decreasing noises and the like (in a case when a primary circuit and a secondary circuit should be insulated), an individual member, such as a transformer, photo-coupler, and the like, has been used conventionally. These members are referred to generally an insulating coupler, or an isolator. For instance, in the field of communication, high insulating performance is required at boundaries between networks and terminals for protecting the network facilities and the terminal devices having high public interests. In order to ensure a high insulating performance, isolators such as small size transformers for communication, and the like have been used. In the field of instrumentation, medical application, and the like, a sensor portion, a signal detecting portion such as signal waveform processing circuit, and a signal processing portion must be separated in order to ensure the safety and anti-noise protection of the human body and the measuring apparatus, the isolator has been used as an insulating and separating means.
When a transformer is used for insulation, decreasing its size has been restricted in comparison with other individual members, because of a restriction in materials and structure used for the transformer. Accordingly, sometimes requirements for portable terminal devices and card type interfaces, which have been developed rapidly in recent years, could not be satisfied sufficiently. In comparison with other individual devices, such as transistors and resistors, the transformer was expensive, and if special material was used for decreasing its size, its price was further increased.
In order to solve the foregoing problems, such as decreasing the size, weight, and price, an isolator using a photo-coupler, which was assembled with a combination of a light emitting element and light receiving element, was invented. However, in the case of a photo-coupler type isolator, the electric characteristics are readily varied depending on external characteristics, such as temperature change, on account of the structural feature of the element, and, if the variation is to be corrected, a correcting circuit, which required precise control, was necessary. In addition to general manufacturing processes for producing the semiconductor device, an extra manufacturing process for producing the light emitting element and the light-receiving element is required. Accordingly, the isolator was generally expensive, and it was difficult to manufacture the light emitting element and the light receiving element simultaneously with the semiconductor device, such as a driving, detecting, correcting circuit, and others.
A capacitive isolator has been developed, in order to decrease the size and price of the isolator. Ceramic capacitors for power or for protecting against surge have been used as individual members for composing an insulating barrier, and a circuit for transmitting signals composed of the above members is called a capacitive insulating amplifier, or a capacitive insulating coupler. A PWM (Pulse Width Modulation) method and others are generally used as the method of transmitting signals via the capacitive insulating barrier, but this method has been applied to the isolator using the insulating transformer and photo-coupler, before this method is applied to the capacitive insulating coupler and the like.
With respect to circuit interface application, such as a modem and the like, U.S. Pat. No. 4,757,528 (hereinafter, called the 528 patent) discloses an idea of making a monolithic semiconductor using a capacitive insulating barrier. JP-A-7-30770 (1995) discloses three capacitive insulating barriers, although they are not monolithic, and a modem application circuit method for digital PWM signal transmission using the same.
The isolator is required further to be decreased in size, weight, and price. In view of these points, the prior art has the following issues and problems.
In accordance with the prior art before the 528 patent, an insulating barrier having a high performance in dielectric withstand voltage includes a signal modulating circuit portion for converting input signals to waveform suitable for transmission and a signal demodulating circuit portion for demodulating the received transmitted signals to the original signals provided as respectively separated components, and the isolator was composed of the plural components mounted on a same package, and the like. Accordingly, the number of the components is large, the assembling steps are complex, and a problem is generated in decreasing its production cost. Because of the need to mold a large number of components into a single package, a problem was generated in decreasing its size.
In accordance with the 528 patent, concurrent use of the capacitive insulating barrier and the PWM transmission method is disclosed as a means for composing the circuit interface, which is an application circuit using a monolithic semiconductor. In accordance with the above manufacturing method, the insulating coupler comprising the capacitive insulating barrier and the PWM circuit is formed on a monolithic semiconductor by a dielectric separating process, and signals in voice band are transmitted. However, the disclosed technology only relates to control of an insulating switch by thermal pulses, and the 528 patent is silent as to what structures of the insulating barrier and the control circuit are used, by what method they are composed, how it operates as a result, and what advantages can be realized.
In accordance with JP-A-7-307708 (1995), a circuit composition, wherein three signals are transmitted by three capacitive insulating barriers, is disclosed, in contrast with using two insulating barriers for one transmission path, conventionally. However, how to operate it for transmitting signals is not indicated. No suggestion for providing a monolithic semiconductor with these circuits including the insulating barriers is proposed.
In case of an isolator of the prior art using transformer and photo-coupler, the ability to reduce its size and price as requested by the market was restricted, on account of the large number of components involved in the mounting operation and the structures of the components themselves. An isolator using a capacitive insulating barrier, which was expected to decrease in size in comparison with the isolator and the like using a transformer, was proposed. However, the capacitive barrier and its transmitting circuit were individual components, and so a decrease in the size was restricted. In a case when these members are composed of multi-chip modules, a problem that the module is expensive was generated.
An idea to compose the peripheral circuits and the capacitive barrier in a monolithic semiconductor structure has been disclosed. However, no practical structure of the capacitive barrier is disclosed, nor is any circuit and its arrangement for using the capacitive barrier disclosed. Accordingly, no practical method and composition are disclosed, nor is any practical technology for realizing a smaller size and a cheaper price disclosed.
The present invention was achieved in consideration of the above problems. The present invention provides insulating barriers having a smaller size and a cheaper price, and having a high insulating performance, and a monolithic isolator IC and application circuit IC, using the insulating barrier.
The present invention provides a method for composing the insulating barrier and its control circuit and peripheral circuits on a semiconductor chip, in which a high dielectric withstand voltage performance between insulated and separated regions is achieved.
The present invention provides design technology for realizing a high dielectric withstand voltage performance, when a semiconductor device composed of monolithic isolator is mounted on an IC package.
The semiconductor device in accordance with the present, invention comprises a semiconductor chip, which comprises a circuit region; a plurality of first terminal electrodes and a plurality of second terminal electrodes, which are connected to the circuit region, respectively; and an insulation region separating electrically the plurality of first terminal electrodes from the plurality of second terminal electrodes, for transmitting signals from a first terminal electrode to a second terminal electrode. Therefore, the semiconductor device becomes small in size, even though it has a preferable insulating performance. Here, by using the semiconductor device according to the present invention with a SOI (Silicon on Insulator) substrate, or dielectric separating substrate, and an insulating groove by trench technology, plural circuit regions are isolated and separated electrically from each other. As a signal transmitting means among the circuit regions, any of a high dielectric withstand voltage capacitance utilizing the insulating groove, a high dielectric withstand voltage capacitance utilizing insulating film between layers, a transformer utilizing the circuit and the insulating film between layers, and the like is used.
When the semiconductor device according to the present invention is practically composed, important points for realizing a decrease in size and price, and a high dielectric withstand voltage performance, are as follows:
(1) In a chip layout of the semiconductor device, wherein insulated and separated plural circuit regions and isolators are made monolithic, the supporting substrate portion of the semiconductor device and the circuit regions are insulated and separated so that the required dielectric withstand voltage at all portions of the semiconductor device can be obtained, in addition to the isolation-separation between the circuit regions.
(2) The areas occupied by respective ones of the insulated and separated circuit regions in the above chip layout of the semiconductor device are designed to be equal to each other, in order to share the voltage equally even if a high voltage is applied between the circuit regions.
(3) When the areas occupied by respective ones of the insulated and separated circuit regions in the above chip layout of the semiconductor device are not equal to each other, an unevenly shared voltage generated when a high voltage is applied between the circuit regions is solved by altering the composition of the insulating grooves for separating the circuits corresponding to the area of the circuit. Furthermore, a region surrounded with the insulating grooves, where electricity is not applied, is provided in the circuit region; an electricity applied region for adjustment is newly provided outside the circuit region; or an external capacitance is connected to the outside of the semiconductor device. Otherwise, the problem of the unevenly shared voltage is solved by concurrent use of the above measures.
(4) In accordance with the above-described chip layout of the semiconductor device, the distance between terminal electrodes requiring a high dielectric withstand voltage among the terminals, the insulating film of which has peeled off, is selected to be a value which does not cause any dielectric breakdown. That is, the layout is designed to obtain the necessary dielectric withstand voltage outside the semiconductor device, in addition to inside the semiconductor device.
(5) In accordance with the above-described semiconductor device, the distance between a bonding wire for electrically connecting the terminal electrode and a lead used in mounting the device in a package, and a part of the semiconductor device (such as openings of a bonding pad, terminal end portions of the semiconductor chip, and others), the insulating film of which has peeled off, is selected to be a value which does not cause any dielectric breakdown.
(6) In accordance with the package whereon the above-described semiconductor device is mounted, the distance between leads requiring insulation and separation from each other is selected to be a value which does not cause any dielectric breakdown. Practically, the distance between inner leads requiring insulation and separation from each other, the distance between the inner lead and the die pad mounted with the semiconductor device, and the distance between outer leads withdrawn from the package each are selected to be a value which does not cause any dielectric breakdown. Naturally, the end portions are designed to have a higher dielectric withstand voltage than the dielectric withstand voltage for the inside of the semiconductor, in order to utilize the performance of the device sufficiently.
In accordance with the present invention, it becomes possible for the first time to provide a semiconductor device, wherein plural circuit regions and isolators insulated and separated are made monolithic, in a condition that the semiconductor device is mounted on an IC package and the like, and is practically usable. By applying the semiconductor devices according to the present invention to modem circuits and terminal devices incorporating the modem circuits therein in the field of communication, these circuits and devices can be decreased in size. The semiconductor device according to the present invention can be applied not only to the field of communication, but also to the field of instrumentation and medical use. For instance, if it is used for insulation, and separation between various sensors and signal processing circuits, the anti-noise property and safety for the human being can be improved.